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Background

In October 2007, methane gas was found in probes installed around the boundaries of the Mallard Lake Landfill in DuPage County, Illinois.

Methane gas was also discovered in soil at a testing location outside the landfill prompting the need for further investigation. In response to these findings, EPA asked the operator of the landfill BFI Waste Systems of North America, to do more sampling. On Nov. 6-10, BFI's contractors sampled for underground gas in the rights-of-way and public spaces outside the western boundaries of the landfill. The results of this sampling showed the presence of high levels of methane in five locations about 40 feet below ground. A shallower sample was taken on Dec. 3 in a public space and methane was discovered about 20 feet down. Methane gas develops naturally as a result of decomposition of landfill waste.

In addition to testing for gases, EPA has asked BFI to sample ground water near the landfill. On Nov. 13 and 15, DuPage County sampled 11 private wells along County Farm Road west of the landfill. No VOCs were detected in any of the water samples from these wells.

At the same time, investigative teams consisting of EPA and BFI contractors, under EPA oversight, began testing homes near the landfill for methane and other gases. Residents were also offered combustible gas indicators. As of Dec. 15, more than 70 homes have been screened and no explosive vapors have been found. More than 50 homes have had combustible gas indicators installed.

On Dec. 4, 2007, EPA entered into a legal agreement with BFI Waste systems of North America, Inc. and the Forest Preserve District of DuPage County to further investigate and address the problems at the landfill. This agreement is called an Administrative Order on Consent or AOC and may be viewed on this web site.

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Site Updates

December 2013

The system in operation today consists of 3 large diameter extraction wells (LDE), 9 passive vent wells (PV series), 24 vacuum curtain (VC series) wells, 5 close proximity extraction wells, and a new blower/flare system. The LDE well system installed inside the Landfill property and outside the limits of waste has been operating since approximately April 1, 2008. The on-site vacuum curtain (VC) wells were installed in November and December 2009, and began operation in February 2010 along the west side. Gas has not been detected in any of the nearly 250 homes that have been monitored in the migration area. Similarly, none of the shallow gas probes (less than 15 feet deep) constructed in residential areas has detected the presence of methane. Methane detection devices have been installed at over 220 residences requesting such services within the affected areas. Sub-slab port gas monitoring has been conducted at seven (including four locations designated by USEPA) locations without identifying any evidence of vertical migration of the landfill gas toward the residences. Currently over 100 on-site and 75 off-site gas monitoring probes are monitored ranging from daily to quarterly. These data are compiled monthly and quarterly in direct response to USEPA requests and continuation of Corrective Action Plan requirements as specified in the Administrative Order on Consent.

October 23, 2013 – AECOM submits Draft Full-Scale Passive Venting Work Plan to USEPA to expand passive venting of off-site west area gas monitoring probes. The work plan is submitted as follow-up to a USEPA request on July 18, 2013.

September 16, 2013 – AECOM submits request to USEPA for approval to conduct a shut down extraction wells GVM-10, GVM-10A, GVM-10B, and GVM-11 as part of a pilot test to evaluate their effectiveness in controlling methane concentrations in the on-site south area.

May 6, 2013 – Passive venting of select off-site west area gas monitoring probes initiated consistent with the Draft Pilot Study Work Plan and discussion with USEPA.

March 29, 2013 – USEPA approves methane trend analysis consistent with the November 4, 2011 proposal. In addition to the data presented in the November 4, 2011 submittal, groundwater elevation (piezometric surface) and static pressure will be included. Data will be submitted on a quarterly basis.

March 5, 2013 – AECOM submits Draft Pilot Study Work Plan to USEPA to passively vent select off-site west area gas monitoring probes. The work plan is submitted as follow-up to an on-site meeting on February 4, 2013, consistent with the previous (October 4, 2011) request to USEPA for approval for passive venting on a continuous basis.